Marine propulsion systems are frequently mounted in environments sensitive to excessive heating. For this reason are exhaust manifolds and turbo units frequently connected to a liquid coolant system.
Examples are provided in U.S. Pat. No. 5,109,668 and U.S. Pat. No. 4,179,884 where marine propulsion systems are described whose exhaust manifolds are surrounded by water jackets for reasons of safety.
U.S. Pat. No. 4,977,741 describes an exhaust system combining an exhaust manifold and exhaust elbow, where the manifold is surrounded by a first water jacket and the elbow by a second water jacket. First and second water jackets are separated by a dam containing a passage for fluid communication between them. This will permit different temperature regions to be established in the exhaust system and prevent the formation of condensate due to excessive cooling of the exhaust gases.
In conventional applications, the coolant is recirculated to the coolant system from the cooling jacket of the exhaust manifold by way of external channels arranged outside of the cylinder head. As a consequence, construction volume is increased and more space is required.